Blade spacer

ABSTRACT

A gas turbine engine blade spacer has an axially extending backbone, spaced apart forward, mid and aft dovetail lands, respectively, disposed along the backbone, the backbone and the forward, mid, and aft dovetail lands having bottom curved backbone surfaces. Each of the forward, mid and aft dovetail lands has a riser that extends above the backbone and has a riser flat top. In the exemplary embodiment disclosed herein, a spacer tab extends generally axially forward of the forward land and includes intersecting axially and radially extending tab apertures. A void extends around the backbone and between the forward and aft dovetail lands and the void is filled with an elastomeric material. The spacer has a constant shape and size cross-section between the forward and aft dovetail lands. The spacer has a particular use with circular arc dovetail slots and roots for which the spacer is a circular arc shaped spacer and the backbone, and the forward, mid and aft dovetail lands are curved along a circular arc normal to and about a radial axis. The spacer tab has a rectangular cross-section, extends axially out of a forward face of the forward land, and has a tab flat top that is co-planar with the riser flat tops of the risers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to gas blade spacers that aredisposed beneath dovetail roots of blades within dovetail slots in gasturbine engine assemblies and, more particularly, to such spacers forfan assemblies having fan blades with circular arc dovetail roots thatmate in circular arc dovetail slots in a disk of a fan rotor.

2. Discussion of the Background Art

A turbofan gas turbine engine used for powering an aircraft in flightincludes a fan assembly having a plurality of circumferentially spacedapart fan blades extending radially outwardly from a rotor disk. Ambientairflow is channeled between the blades and pressurized, thereby,generating thrust for powering the aircraft in flight. The fan assemblytypically includes a plurality of circumferentially spaced apart fanblades, each having a dovetail root disposed in a complementary, axiallyextending dovetail groove or slot in a perimeter or rim of a rotor disk.The dovetail slots are defined by dovetail posts and are complementaryin configuration with the blade dovetail roots for radially retainingthe blades to the rotor disk. The blades are also axially retained inthe rotor disk to prevent axial movement of the blades in the upstreamand downstream directions. A spacer fills the balance of the space belowthe blade root within slot.

During a bladeout event, a blade or portion of blade is released andimpacts the first trailing blade adjacent the damaged blade causing thefirst trailing blade to rotate circumferentially. The present inventionis particularly useful for fan assemblies with circular arc dovetailroots and slots. This makes the dovetail load up on point locationswhich jeopardized the integrity of the dovetail. The blade needs to beprevented from rotating too much and loading the corners up. When theblade tends to rotate, the spacer gets pinched between the bottom of theblade root and the bottom of the slot in the disk, thus, preventingrotation. The rotational moment is shared by a majority of the pressureface instead of on the corner points of the dovetail root.

A fan disk assembly for a low radius hub design incorporating a circulararc dovetail root and slot to ensure an adequate footprint and load pathinto the disk has been developed. This design is used for increasing theairflow through the fan blades to increase the thrust without increasingor holding to a limit of a tip of the fan blade. An inner flowpathboundary, often referred to as the hub, is moved radially inwardly froman existing engine design or the engine is originally designed to have,what is referred to as, a low radius hub. Conventionally, a radialtransition portion is a transition from a curved blade section at theflowpath to a straight shank at the top of the dovetail. Due to the lowinner diameter of the flow path, the radial transition portion of thefan blade from the aerodynamic or curved portion of the blade to thedovetail root is significantly shortened. It is highly desirable to havean improved spacer for a low radius hub design which incorporates acircular arc dovetail root and slot to ensure adequate blade retentionfor the first trailing blade adjacent the damaged blade during abladeout event.

SUMMARY OF THE INVENTION

A gas turbine engine blade spacer has an axially extending backbone,spaced apart forward, mid and aft dovetail lands, respectively, disposedalong the backbone, the backbone and the forward, mid, and aft dovetaillands having bottom curved backbone surfaces. Each of the forward, midand aft dovetail lands has a riser that extends above the backbone andhas a riser flat top. In the exemplary embodiment disclosed herein, aspacer tab extends generally axially forward of the forward land andincludes intersecting axially and radially extending tab apertures. Avoid extends around the backbone and between the forward and aftdovetail lands and the void is filled with an elastomeric material. Thespacer has a constant shape and size cross-section between the forwardand aft dovetail lands.

The invention has a particular use with circular arc dovetail slots androots for which the spacer is a circular arc shaped spacer and thebackbone, and the forward, mid and aft dovetail lands are curved along acircular arc normal to and about a radial axis. The spacer tab has arectangular cross-section, extends axially out of a forward face of theforward land, and has a tab flat top that is co-planar with the riserflat tops of the risers.

In one particular embodiment, the invention is a spacer in a gas turbineengine rotor disk assembly having a number of annular hubs circumscribedabout a centerline, each of the hubs connected to a disk rim by a web,and a plurality of circumferentially spaced apart dovetail slotsdisposed through the rim. The dovetail slots extend circumferentiallybetween disk posts, axially from a forward end to an aft end of the rim,and radially inwardly from a disk outer surface of the rim. A pluralityof fan blades have dovetail roots which are disposed in the dovetailslots and corresponding ones of the blade spacers which are disposed inthe dovetail slots between a dovetail slot bottom wall and an axiallyextending root bottom surface of each of the dovetail roots.Circumferentially extending annular burst slots extend radially throughthe rim into the dovetail slots between each adjacent pair of the webs.The forward, mid, and aft dovetail lands, respectively, are locatedalong the backbone such that the burst slots are located between theforward, mid, and aft dovetail lands.

In yet a more particular embodiment of the invention, pairs ofcircumferentially oppositely facing retaining slots extend throughoverhangs of circumferentially adjacent pairs of the disk posts at anaxial location where the overhangs begin extending axially forward fromthe rim. Retainers are disposed in the pairs of retaining slots andextend across the dovetail slot so as to axially retain the dovetailroots in the dovetail slots. Each of the retainers is radially supportedby a corresponding one of the spacers and each of the retainers includesa rectangular slot through which is disposed a corresponding one of thespacer tabs. Each retainer includes a shelf radially below the slot andupon which the spacer tab rests. A radially extending shelf aperture isdisposed through the shelf and aligned with the radially extending tabaperture. A spacer bolt having a spacer bolt head and a threaded spacerbolt shank is disposed through the shelf aperture and the radiallyextending tab aperture such that the spacer bolt head engages the shelf.A spacer nut is threadingly secured on the spacer bolt shank such thatthe spacer nut engages the spacer tab.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the present invention areset forth and differentiated in the claims. The invention is moreparticularly described in conjunction with the accompanying drawings inwhich:

FIG. 1 is a cross-sectional view illustration of a forward section of aturbofan gas turbine engine, partly in section, illustrating anexemplary fan assembly of the present invention.

FIG. 2 is an exploded perspective view illustration of a fan rotor inthe fan assembly illustrated in FIG. 1.

FIG. 3 is a perspective view illustration of a fan disk in FIG. 1.

FIG. 4 is an enlarged cross-sectional view illustration of the fan diskin FIG. 3.

FIG. 5 is a cross-sectional view illustration of the fan disk rotorillustrated in FIG. 2 mounted to a booster rotor section of the forwardsection of the turbofan gas turbine engine illustrated in FIG. 1.

FIG. 6 is a forward looking aft perspective view illustration of aspinner of the fan rotor illustrated in FIG. 1.

FIG. 7 is an aft looking forward perspective view illustration of thespinner of the fan rotor illustrated in FIG. 1.

FIG. 8 is an enlarged cross-sectional view illustration of the spinnerof the fan rotor illustrated in FIG. 1.

FIG. 9 is a cross-sectional view illustration of a dovetail slot in thefan disk in FIG. 3.

FIG. 10 is an enlarged perspective view illustration of a portion of thefan disk in FIG. 3.

FIG. 11 is a cross-sectional view illustration of a lower portion of thefan blade with fan blade lightening holes mounted in the dovetail slotin the fan disk in FIG. 1.

FIG. 12 is an enlarged perspective view illustration of a forwardportion of the fan disk in FIG. 10.

FIG. 13 is a perspective view illustration of a spacer in the dovetailslot of the fan disk in FIG. 10.

FIG. 14 is a perspective view illustration of a forward portion of thespacer in FIG. 13 engaged with a retainer in the fan disk in FIG. 1.

FIG. 15 is a forward looking aft perspective view illustration of theretainer in FIG. 14.

FIG. 16 is an aft looking forward perspective view illustration of theretainer in FIG. 14.

FIG. 17 is a cross-sectional view illustration of forward seal and aftseals in the fan disk in FIG. 1.

FIG. 18 is a radially inwardly looking sectional view illustration ofthe forward seal in FIG. 17.

FIG. 19 is a forward looking aft perspective view illustration of a fanplatform of the fan rotor illustrated in FIG. 1.

FIG. 20 is a radially inwardly looking sectional view illustration ofthe fan platforms assembled on the fan rotor illustrated in FIG. 1.

FIG. 21 is a radially outwardly looking perspective view illustration ofthe fan platform illustrated in FIG. 19.

FIG. 22 is a cross-sectional view illustration of the spacer throughline 22—22 in FIG. 13.

FIG. 23 is a cross-sectional view illustration of the spacer throughline 23—23 in FIG. 13.

FIG. 24 is a cross-sectional view illustration of the spacer throughline 24—24 in FIG. 13.

FIG. 25 is an enlargement of a portion of the fan disk within thephantom line circle in FIG. 5.

FIG. 26 is an exploded perspective view illustration of seals on the fanplatform illustrated in FIG. 20.

FIG. 27 is a cross-sectional view illustration of the platform throughline 27—27 in FIG. 26.

FIG. 28 is an enlargement of the portion of the fan disk within thephantom line circle in FIG. 4.

FIG. 29 is an enlargement of the portion of the fan disk within thephantom line circle in FIG. 5.

DETAILED DESCRIPTION

Illustrated schematically in FIG. 1 is a forward portion of an aircraftturbofan gas turbine engine 10 including an exemplary embodiment of arotor assembly of the present invention in the form of a fan assembly 12which is rotated by a fan drive shaft 14 powered by a low pressureturbine (not shown). The fan assembly 12 includes a fan rotor disk 16from which extends radially outwardly a single axially located row 18 ofcircumferentially spaced apart fan blades 20. Disposed downstream of thefan assembly 12 is a conventional booster compressor 26 having axiallyspaced apart rows of booster vanes 22 and rows of booster blades 24mounted on a rotatable booster spool 28. An annular mounting plate 29has annular pluralities of radially inner apertures 174, radially outerapertures 208, and radially mid apertures 23 radially located betweenthe radially inner apertures and outer apertures. The annular mountingplate 29 is bolted or otherwise fixedly connected to the booster spool28 with a plurality of plate bolt assemblies 25. Each of the plate boltassemblies 25 has a carriage bolt 37 disposed through one of the midapertures 23 and one of a plurality of spool apertures 19 in the boosterspool 28. Each of the carriage bolts 37 has a bolt head 21 engaging themounting plate 29 and attached to a shank 476 with a threaded free end478 and a smooth portion 480 between the bolt head 21 and the free end478. The smooth portion extends through the mid aperture 23 and thespool aperture 19. The carriage bolt 37 is secured by a countersunk nut33 screwed onto the free end 478 to connect the booster spool 28 to theplate 29. Interference fits between the countersunk nuts 33 and themounting plate 29 holds the nuts in place when the bolt heads 21 aretorqued to tighten the plate bolt assemblies 25.

The mounting plate 29 is fixedly connected to the rotor disk 16 by aplurality of inner bolt assemblies 30 as shown in more particularity inFIGS. 5 and 17. Thus, the booster spool 28 is connected to the rotordisk 16 via the mounting plate 29 and the mounting plate is consideredpart of the booster spool. The booster spool and the fan disk arerotated by a turbine (not shown) through the fan drive shaft 14. The fandrive shaft 14 is rotatably supported within static structure or frame38 of the engine by a thrust bearing 43.

Referring further to FIGS. 2 and 3, each of the fan blades 20 has acurved airfoil section 56 with pressure and suction sides 55 and 57,respectively, extending between airfoil leading and trailing edges LEand TE, respectively. The airfoil section 56 is attached to a circulararc dovetail root 58 and a transition section 60 of the fan blade 20extends between the airfoil section and the root. Referring further toFIG. 4, the fan rotor disk 16 is a multi-bore disk having a rim 62attached to a number of disk hubs 64 with bores 66 by a correspondingnumber of webs 68 circumscribed about the centerline 11. Web channels 61extend axially between the webs 68 and radially between the rim 62 andthe hubs 64.

Three identical hubs are used in the exemplary embodiment of theinvention illustrated herein, a different number of hubs may be usedsuch as 2 or 4 or more. The disk of the invention is not limited toidentical hubs, webs, and bores. The hubs, webs, and bores can havedifferent radial and axial dimensions. Because the fan blade 20 has along axial length L relative to an outer diameter of the disk 16, notedby a radial distance R1 from a disk outer surface 63 to the enginecenterline 11, a multi-bore disk is more efficient than the traditionalsingle bore disk due to its lighter weight. The multi-bore disk of thepresent invention may also be used in other parts of the engine such asin a compressor or turbine.

Referring to FIG. 4, note that the rim 62 is radially spaced very closeto the hubs 64. The web channels 61 are wide and short compared to thosein conventional disks. The webs channels have relatively wide channelmaximum widths W1, extending axially between the webs 68, compared torelatively short channel lengths LC extending radially between the rim62 and the hubs 64.

The channel maximum width W1 is on the same order of magnitude as thechannel length LC. The web channels 61 are substantially rounded and thewebs 68 have relatively large radially inner and outer fillets 71 and73, respectively, and the inner fillet 71 extends in a range of about30-70 percent of the channel length LC and is illustrated in theexemplary embodiment as being about 50 percent of the channel length LC.The web channels are short and wide and, in the exemplary embodiment,the webs 68 are formed substantially by the inner and outer fillets 71and 73 which have large inner and outer radii of curvature 75 and 77,respectively. In general, the inner and outer fillets 71 and 73 form asubstantial portion of the web 68. The inner fillets 71 are large andhave a large inner radius of curvature 75 to avoid large stressconcentrations that can build up between the hubs 64 and the webs 68.

Referring further to FIGS. 2, 3 and 4, a plurality of circumferentiallyspaced apart circular arc dovetail slots 52 are disposed through the rim62 and extend circumferentially between disk posts 50, axially from aforward end 65 to an aft end 67 of the rim, and radially inwardly fromthe disk outer surface 63 of the rim. The circular arc dovetail slots 52are used for receiving and radially retaining the circular arc dovetailroots 58.

The circular arc dovetail root 58, the circular arc dovetail slots 52,and the disk posts 50 are arcuate and curved normal to and about aradial axis RA. This is exemplified by an arc AR through the disk post50 which is circumscribed about the radial axis RA at a radius ofcurvature R. Each of the circular arc dovetail roots 58 is designed toslide axially aftwardly along an arc into a corresponding one of aplurality circular arc dovetail slot 52 and be retained radially andcircumferentially by the disk rim 62 and, more particularly, by theposts 50.

Each of the posts 50 has an overhang 69 extending axially forwardly fromthe disk rim 62 and are located radially outwardly on the posts. In theexemplary embodiment, the disk outer surface 63 of the rim 62 iscontiguous with the disk posts 50 and the overhangs 69. Though thesliding motion is circular along an arc, it is also referred to hereinas an axially sliding motion.

Referring to FIG. 9, conical undercuts 74 are formed in the disk posts50 within and along the circular arc dovetail slot 52. The undercuts 74extend between a conical dovetail slot pressure surface 76 on the diskpost 50 and the rounded cross-sectional or toroidal portion within andalong the circular arc dovetail slot 52. The conical dovetail slotpressure surface 76 is designed to contact a conical dovetail rootpressure surface 78 on the circular arc dovetail root 58. The undercuts74 are conical and, in the exemplary embodiment, are illustrated ashaving an undercut angle 81 with respect to the dovetail slot pressuresurface 76 on the disk post 50 of about 30 degrees. The contact stressesalong root in the arc of contact are high during high speed rotation ofthe fan blades 20 such as during acceleration of the engine and takeoffof the aircraft. The undercuts on the posts 50 help alleviate edge ofcontact stresses.

Referring to FIGS. 1, 4 and 5, the rim 62 has circumferentiallyextending annular burst slots 70 between each adjacent pair 72 of thewebs 68. The burst slots 70 extend radially through the rim 62 into thedovetail slots 52 and provide crack arrestment. The burst slots 70provide severed hoop load paths between rim portions 82 of the rim 62from which the webs 68 depend from the rim 62 which resist crackpropagation from one rim portion 82 of the disk 16 to another. In theexemplary embodiment, the burst slots 70 have a cross-section in theshape of an ogive 85 with a radially outer ogive radius 83 and aradially inner ogive radius 84 wherein the radially inner ogive radiusis substantially larger.

Referring further to FIG. 5, an annular forward extension 86 (acylindrical annular forward extension exemplified herein) has an annularforward flange 90 and an annular aft extension flange 87. The aftextension flange 87 is bolted to an annular forward arm 89 extendingforward from a forward most one 88 of the webs 68 of the disk 16.Alternate embodiments include the forward extension 86 being integrallyformed or cast with and extending forward from the forward most one 88of the webs 68 of the disk 16. An annular aft arm 96 (a conical annularaft arm exemplified herein) extends axially aftwardly from and isintegrally formed or cast with an aftward most one 98 of the webs 68 ofthe disk 16 and has an annular aft flange 94. The annular aft flange 94is bolted to the fan drive shaft 14 as illustrated in FIG. 1, thus,connecting the fan disk to the fan drive shaft.

The forward flange 90 is scalloped having a plurality ofcircumferentially distributed forward bolt holes 100 through lobes 101between scalloped out sections of the forward flange. A plurality ofcircumferentially distributed extension lightening holes 102 aredisposed through the forward extension 86 to reduce weight of the disk16 and fan assembly 12. The forward extension 86 is designed withsufficient flexibility and length to attenuate or accommodatedifferential radial growth between the disk 16 and a spinner 104.

Illustrated in FIGS. 2, 3, 4, 5, 19 and 20 are non-integral platforms 32(separate from the fan blades 20) circumferentially disposed between thefan blades 20. Forward and aft disk lugs 34 and 35, respectively, extendradially outwardly from the posts 50 along the disk outer surface 63 ofthe rim 62 of the disk 16. Each of the platforms 32 has anaerodynamically contoured platform wall 27 with a radially outer surface36 which faces radially outwardly and defines and maintains an inner fanflowpath that extends axially across the fan blade 20. A radially innersurface 236 of the platform wall 27 faces radially inwardly. Theplatform walls 27 are sloped with respect to the centerline 11 toprovide an increasing radius of the outer surface 36 (the inner fanflowpath surface along the platform) in the axially aft direction.

A radially outer corner 45 of the disk post 50 has a flat chamfer 39which encompasses a portion of the overhang 69 of the disk post. Theplatform walls 27 are angled or sloped parallel to the chamfer 39. Inthe exemplary embodiment illustrated herein, the platform walls 27 areparallel to and spaced apart a first clearance C1, illustrated in FIG.5, of about 30 mils (0.03 inches) from the chamfer 39 along the radiallyouter corner 45 of the overhang 69 of the disk post 50. Furtherreferring to FIG. 21, a wedge shaped platform bumper 238 dependsradially inwardly from the inner surface 236 of the platform wall 27.The platform bumper 238, in the exemplary embodiment, has a flat bottomsurface 240 and there is about a 50 mil second clearance C2, illustratedin FIG. 5, between the bottom surface and the inner surface and diskouter surface 63 along the post 50. The platform bumper 238, in analternative embodiment, may have a circumferentially curved bottomsurface contoured to match the circumferentially curved disk outersurface 63.

Referring to FIGS. 19 and 20, the platform walls 27 have a rectangularlyshaped forward portion 252 and a circumferentially curved aft portion244. The circumferentially curved aft portion 244 is contoured to fitaround the curved airfoil section 56 between the airfoil leading andtrailing edges LE and TE, respectively. The circumferentially curved aftportion 244 has pressure and suction side edges 262 and 264,respectively, which are shaped to conform to the pressure and suctionsides 55 and 57, respectively, of the airfoil section 56.

Each of the platforms 32 has forward, mid, and aft mounting lugs 40, 42,and 44, respectively, depending radially inwardly from the platform wall27. The forward and aft mounting lugs 40 and 44 are located at forwardand aft ends 46 and 48, respectively, of the platform walls 27 and themid mounting lug 42 is axially located therebetween, though, notnecessarily midway. The mid and aft mounting lugs 42 and 44 have axiallyextending mid and aft holes 47 and 49, respectively, therethrough andbushings 41 disposed within the mid and aft holes. Platform materialsare typically an aluminum alloy such as 7075-T73 Aluminum, which cannottake a large bearing stress imposed on it by pins used to radiallysecure or retain the platforms 32 to the disk 16 when the fan is runningat high speeds. The inside of the holes in the platform lugs would crushunder the bearing load of the pins. Therefore, the exemplary embodimentof the present invention incorporates the press-fit bushings 41 in themid and aft holes 47 and 49 of the platform 32. The bushings 41 are madeof a harder material with the necessary bearing capability such asInconel 718. The bushings 41 are pressed into the holes with aninterference on the order of 1.5-2.5 mils on diameter. Thus, the bearingstress imparted by the pins is attenuated through the bushings and doesnot adversely affect the aluminum platform.

The rectangularly shaped forward portion 252 of the platform wall 27includes a platform leading edge 140 extending axially forward just pastthe rim 62 and the forward mounting lug 40 depending from the forwardportion 252 at the platform leading edge over and flush with a forwardfacing circular rim surface 142 as illustrated in FIGS. 5 and 25. Aplurality of post holes 214 extend axially aftwardly into the circularrim surface 142 at the front of the rim 62. Each post hole 214 extendsinto a corresponding one of the disk posts 50.

Each of the forward mounting lugs 40 has a forward lug aperture 51 tosupport a corresponding one of a plurality of aftwardly extendingplatform pins 220. Each platform pin 220 has a smooth cylindrical body222 attached to a narrower shank 224. The shank 224 has a threaded freeend 226 and a smooth portion 228 between the smooth cylindrical body 222and the free end 226. The smooth portion 228 is disposed through theforward lug aperture 51 to provide a good smooth cylindrical loadbearing surface in contact with the forward mounting lug 40. The smoothportion 228 is as long as the width or thickness of the forward lugaperture 51. An internally threaded countersunk nut 230 is screwed ontothe free end 226 to secure the platform pin 220 to the forward mountinglugs 40. The countersunk nut 230 has a small unthreaded portion 232 witha countersink before threads in the nut.

Referring to FIGS. 5 and 25, a deep first counterbore 152 axiallyextends through each of the forward disk lugs 34 up to a back wall 144of the counterbore at an aft end 156 of the forward disk lug. A firstbolt hole 154 that is co-axial with the first counterbore 152 axiallyextends through the back wall 144. A forward pin 150 also has a smoothcylindrical body 157 attached to a narrower shank 161 as discussedabove. The shank 161 has the threaded free end 158 and a smooth portion159 between the smooth cylindrical body 157 and the free end 158. Thesmooth cylindrical body 157 of the forward pin 150 is tightly disposedin the first counterbore 152. The narrower smooth portion 159 of theforward pin 150 is disposed through first bolt hole 154 that axiallyextends through the back wall 144 of the forward disk lugs 34. Thesmooth cylindrical body 157 and the first counterbore 152 havesubstantially the same first diameter 160, the first bolt hole 154 has asecond diameter 162, and the first diameter is larger than the seconddiameter. An internally threaded countersunk nut 164 is screwed onto thefree end 158 of the shank 161 to secure the forward pin 150 to theforward disk lug 34.

An aft aperture 170 axially extends through each of the aft disk lugs 35and aligns with a corresponding one of the inner apertures 174 in theannular mounting plate 29. Each of the inner bolt assemblies 30 has acarriage bolt 180 disposed through the aft aperture 170 and the inneraperture 174. Each of the carriage bolts 180 has a bolt head 182engaging the aft disk lugs 35 and attached to a shank 176 with athreaded free end 178 and a smooth portion 188 between the bolt head 182and the free end 178. The smooth portion extends through the aftaperture 170 and the inner apertures 174. The carriage bolt 180 issecured by a countersunk nut 190 screwed onto the free end 178 toconnect the aft disk lugs to the plate 29. Interference fits between thecountersunk nuts 190 and the mounting plate 29 holds the nuts in placewhen the bolt heads 182 are torqued to tighten the inner boltassemblies.

A plurality of forwardly extending aft pins 200 are mounted upon theannular mounting plate 29. Each aft pin 200 has a smooth cylindricalbody 202 attached to a narrower shank 204. The shank 204 has a threadedfree end 206 and a smooth portion 207 between the smooth cylindricalbody 202 and the free end 206. The smooth cylindrical body 202 extendsaxially forward of the plate. The smooth portion 207 is disposed througha corresponding one of the radially outer apertures 208 in the annularmounting plate 29. An internally threaded countersunk nut 210 is screwedonto the free end 206 to secure the aft pin 200 to the annular mountingplate 29. The countersunk nut 210 has a small unthreaded portion 232with a countersink before threads in the nut. Each of the aft pins 200is disposed in a corresponding one of the aft holes 49 in the aftmounting lugs 44.

Referring again to FIGS. 19, 20 and 21, circumferentially curved aftstiffening ribs 270 extend between the mid and aft mounting lugs 42 and44. The aft stiffening ribs 270 extend substantially parallel to andspaced a first distance 272 inwardly from the pressure and suction sideedges 262 and 264, respectively. Circumferentially curved forwardstiffening ribs 271 extend axially from the mid mounting lug 42 to aforward edge 274 of the platform bumper 238, about where the wedgeshaped platform bumper 238 begins to depend radially inwardly from theinner surface 236 of the platform wall 27. The forward stiffening ribs271 are tapered or blended down to the inner surface 236 of the platform32, such that at any axial position, the height of the forwardstiffening ribs is less than the height of the platform bumper 238 alongan axially extending bumper length 239. The platform bumper 238 providesadditional stiffness to control the stress and deflection of theplatform 32 and platform wall 27 during ice or bird impacts in thisregion. The platform bumper 238 creates a load path from the thinplatform wall 27 into the top of the disk post 50 and limits deflections(and thus stresses) in case of such an impact event.

Each of the platforms 32 is mounted on the disk 16 between two adjacentones of the fan blades 20. First, two adjoining fan blades are mountedon the disk 16 by circularly sliding the dovetail roots 58 into thecorresponding dovetail slots 52 until a notch 59 (see FIGS. 5 and 17) inthe transition section 60 of the fan blade 20 contacts the annularmounting plate 29. Thus, the annular mounting plate 29, considered partof the rotatable booster spool 28, provides aftwardly axial retention ofthe fan blade 20. Then a platform 32 is mounted on the disk in betweenthe two adjacent mounted fan blades 20 by circumferentially aligning theplatform pin 220, the forward pin 150, and the aft pin 200 with thecorresponding post holes 214 and bushings 41 in the mid and aft holes 47and 49, respectively, and sliding the platform axially aftwardly suchthat the pins are inserted into their corresponding holes and bushings.This essentially forms a pin and clevis means for radially andcircumferentially retaining the platform 32 to the disk 16, the plate29, and the booster spool 28.

Referring to FIGS. 9, 12 and 13, a circular arc shaped spacer 290 isdisposed within each of the dovetail slots 52 between a dovetail slotbottom wall 292, between the disk posts 50, and an axially extendingroot bottom surface 296 of the fan blade dovetail root 58 for exerting aradially outwardly directed force or pre-load upon the blade dovetailroot in order to limit relative motion between the rotor blade and therotor disk. The spacer 290 includes a backbone 300 with forward, mid andaft dovetail lands 302, 304 and 308, respectively, disposed alongbackbone. The backbone 300 and the forward, mid, and aft dovetail lands302, 304 and 308, respectively, have bottom curved backbone surfaces 310continuous and co-extensive with the dovetail slot bottom wall 292. Eachof the forward, mid and aft dovetail lands 302, 304 and 308 has a riser312 that extends radially above the backbone 300 and has a flat top 314.A spacer tab 320 extends generally axially forward of the forward land302 and includes intersecting axially and radially extending tabapertures 316 and 318, respectively. The spacer tab 320 has arectangular cross-section 321 and extends out of forward face 322 of theforward land 302. The spacer tab 320 also has a flat top 324 that isco-planar with the flat tops 314 of the risers 312 of each land. Thespacer's backbone 300, and forward, mid and aft dovetail lands 302, 304and 308, and the spacer tab 320 are curved along a circular arc normalto and about the radial axis RA extending radially from the enginecenterline 11. In the exemplary embodiment, the spacer tab 320 is curvedalong a circular arc normal as described above, in alternativeembodiments, it can be at an angle or straight as it extends out offorward face 322 of the forward land 302. The mid dovetail land 304 hasa spacer undercut 340, about 6 degrees in the exemplary embodimentillustrated herein and other angles may be used, to allow up to 6degrees of controlled rotation to the blade. Once the mid dovetail land304 of the spacer contacts the dovetail slot bottom wall 292, the bladeis then limited in circumferential rotation. The middle spacer isdesigned to work in conjunction with a bladeout bumper 400 on the diskrim that also allows up to 6 degrees of rotation away from the bladeshank. The bladeout bumper 400 and the spacer undercut 340 are designedto contact at the same time and act in parallel to limit the rotation ofthe blade to 6 degrees.

In one embodiment, a void 330 around the spacer's backbone 300 andbetween the forward and aft dovetail lands 302 and 308 is filled with anelastomeric material 332 to provide a soft interference with the disk bysurrounding the parent metal of the backbone spacer 290 with theelastomeric material as illustrated in FIGS. 13, 22, 23 and 24. With thevoid filled, the spacer has continuous axially extending curved edges319 that smoothly arcs the curved normal to and about the radial axisRA. The filled void also provided the spacer with a constant shape andsize cross-sectional area A between the forward and aft dovetail lands302 and 308. This soft interference provides some anti-rotationcapability for the blade by keeping the pressure faces in full contact.The forward, mid and aft dovetail lands 302, 304 and 308, respectively,are disposed along the backbone 300 such that the burst slots 70 arelocated between the forward, mid, and aft dovetail lands 302, 304, and308 so that dovetail lands fully contact metal of the disk asillustrated in FIG. 10.

The spacer is provided to hold the blades radially outwardly and toprevent unwanted rotation and failure of trailing fan blades during abladeout event when a released fan blade impacts a first trailing fanblade. The first trailing blade rotates circumferentially and, in thecase of a circular arc dovetail, it causes a dovetail load up on pointlocations which jeopardized the integrity of the dovetail of the firsttrailing blade. The blade needs to be prevented from rotating too muchand loading the corners up.

The spacer 290 is slid into the dovetail slot 52 between the dovetailslot bottom wall 292 and the root bottom surface 296 of the fan bladedovetail root 58 after the fan blade 20 and the two adjacent platformshave been on the rim 62 of the disk 16. Pairs of circumferentiallyoppositely facing retaining slots 352 are cut through the overhang 69 ofcircumferentially adjacent disk posts 50 at an axial location in anaftwardmost end of the overhang 69 where the overhang 69 of the diskpost 50 begins to extend axially forward from the rim 62. The spacer 290is slid aftwardly till the tab 320 clears the retaining slots 352.Afterwards, referring to FIG. 12, a retainer 350 is used to axially lockfan blade 20 in place.

Note that the spacer may also be straight for use in a straight dovetailslot. In such an embodiment, the backbone is straight and the forward,mid and aft dovetail lands would be axially straight and disposedaxially along the backbone.

Referring to FIGS. 14, 15 and 16, the retainer 350 is generally amonolithic block 360 having a block thickness D1 with a retainer wall362 depending radially inwardly from the block and having a smallerretainer wall thickness D2. A rectangular shelf 364 normal to andextending axially forward of the retainer wall 362 is disposed along aradially inner edge 366 of the retainer wall. In the exemplaryembodiment, the retainer slot 368 is rectangular and disposed throughthe retainer wall 362 along the rectangular shelf 364. The retainer slot368 has a shape and size to allow the spacer tab 320 to be slid throughthe slot. In the exemplary embodiment illustrated herein, the retainerslot 368 is arced or curved sideways and, in an alternative embodiment,is skewed with respect to a shelf centerline 365 extending axially downthe middle of the shelf 364. The spacer tab 320 is also curved and, inan alternative embodiment, skewed with respect to the shelf centerline365 as can be seen in FIG. 10. A radially extending shelf aperture 370is disposed through the rectangular shelf 364 and located to align withthe radially extending tab aperture 318. A raised retainer land 371extends aftwardly off a retainer backside 374 of the retainer 350. Theretainer land 371 has a shape designed to effectively contact an axiallyforward facing flat 414 along the dovetail root 58 as illustrated inFIGS. 17 and 18. Before the retainer 350 is installed, a forward seal410 is installed between the blade 20, the forward stiffening ribs 271and the platform, and trapped in place by the retainer 350. The forwardseal 410 closes potential leak paths at the leading edge of the bladewithout introducing complications to platform side seals bonded to thepressure and suction side edges 262 and 264, respectively, of theplatform 32.

After the spacer 290 is slid aftward in the dovetail slot 52, theretainer is raised from under the overhang 69 of the disk posts 50 intothe circumferentially oppositely facing retaining slots 352. When theretainer 350 is in place in the retaining slots 352, it extends acrossthe dovetail slot 52 axially retaining the fan blade dovetail root 58 inthe dovetail slot 52. The spacer 290 is slid forward and the rectangularspacer tab 320 slides into the retainer slot 368. This can beaccomplished using a tool that easily engages and disengages the spacertab 320 through the axially extending tab aperture 316. The spacer tab320 and the spacer 290 are positioned such that the shelf aperture 370is aligned with the radially extending tab aperture 318. Then a spacerbolt 373 having a spacer bolt head 379 and a threaded spacer bolt shank376 is inserted through the bottom of the shelf aperture 370 and upwardsthough the radially extending tab aperture 318. A spacer nut 378 is thenthreaded and tightened onto the spacer bolt shank 376 such that thespacer nut engages the spacer tab 320 and the spacer bolt head 379engages the rectangular shelf 364.

Referring to FIGS. 26 and 27, platform side seals denoted and referredto herein as pressure and suction side angled seals 403 and 401,respectively, have flat seal bases 402 attached or bonded, such as withan epoxy, to and axially extending along the inner surface 236 of theplatform 32. Pressure and suction side angled seals 403 and 401 aredisposed between the aft and forward stiffening ribs 270 and 271 and thepressure and suction side edges 262 and 264, respectively. Angled seallegs 404 depend radially inwardly from the seal bases 402. The pressureand suction side angled seals 403 and 401 have a cross-section thatchanges along the axial length of the angled seals to conform to theshape of the fan blade 20 against which it seals.

Referring to FIGS. 17 and 18, before the retainer 350 is installed, aforward seal 410 is inserted in an annular space 412 formed between theblade 20, the forward stiffening ribs 271 of adjacent platforms 32, andthe inner surface 236 of the adjacent platforms, the axially forwardfacing flat 414 along the dovetail root 58, and a rabbet 416 between theforward facing flat 414 and the leading edge LE of the airfoil section56. The forward seals 410 in the exemplary embodiment are cylindrical inshape. Each of the forward seals 410 is inserted up through theretention slots 352 to rest between and seal against the blade 20, theforward stiffening ribs 271 of the pressure and suction side edges 262and 264 of adjacent platforms 32, and the inner surfaces 236 of theadjacent platforms 32. Afterwards, the retainer 350 is installed. Theforward seals 410 and the pressure and suction side angled seals 403 and401 are made of silicon or some other elastomeric material.

An annular aft seal 430 is attached or bonded, such as with an epoxy, tothe annular mounting plate 29. The aft seal 430, in the exemplaryembodiment, has a circular cross-sectional shape such that the aft sealmay be described as a hoop. The aft seal 430 is disposed along theannular mounting plate 29 and radially inwardly of the platforms 32 soas to seal a gap defined by the mounting plate, the trailing edge TE ofthe blade 20, and adjacent platforms around the blade.

Referring to FIGS. 2, 3, 9 and 10, the fan disk soft bladeout bumper 400is disposed on the forward disk lug 34 to prevent a fan blade 20released during a bladeout event from impacting an adjacent trailing fanblade. The bladeout bumper 400 includes a circumferentially extendingappendage 440 on the forward disk lug 34 and extends toward the suctionside 57 of the airfoil section 56 of the fan blade 20, illustrated inphantom in FIG. 10. The adjacent trailing fan blade rotatescircumferentially and, for a fan blade with a circular arc dovetailroot, the rotation causes the dovetail root to load up on pointlocations which jeopardize the integrity of the dovetail root. The bladeneeds to be prevented from rotating too much and loading the corners up.The bladeout bumper 400 is designed to work with a fan blade 20 that hasfan blade lightening holes 432 such as illustrated in FIG. 11. Thebladeout bumper 400 is located axially to ensure that the contact ismade at an axial contact location 434 between the fan blade lighteningholes 432 instead of at a fan blade lightening hole. To further ensureminimal loading, the bladeout bumper 400 is wider than previous similarbumpers and axially spans from a hole centerline 435 of one fan bladelightening hole 432 to the hole centerline of an adjacent fan bladelightening hole. The circumferentially extending appendage 440 includesa circumferentially facing bumper surface 442 that faces the suctionside 57 and has a soft coating 436 made of a metallic material such asmetallic thermal spray material. The soft coating 436 is designed tocontact the fan blade 20 and the coating is made of a material softerthan the material of the fan blade, thus, limiting damage to the blade.In the exemplary embodiment, the bumper surface 442 is contoured to theshape of the blade 20 at a location at the axial contact location 434.

Referring to FIGS. 6, 7 and 8, the spinner 104 is attached to theforward flange 90 of the forward extension 86 and, thus, is connected tothe disk 16. The spinner 104, as illustrated in the exemplary embodimentherein, has a hollow body with a substantially conical shape and is asingle piece spinner. The spinner 104 has tip 106 from which a forwardconical section 107 extends aftwardly to transition section 108. An aftconical section 109 extends aftwardly from the transition section 108.The forward and aft conical sections 107 and 109 have different coneangles. A plurality of bosses 110 are circumferentially distributedaround an inner surface 112 of spinner 104 illustrated herein at anaxial location generally corresponding to a location within thetransition section 108 between the forward and aft conical sections 107and 109 of the spinner. A plurality of boss counterbores 117 axiallyadjacent and forward of and co-axial with boss bolt holes 118 in thespinner 104.

Each of the boss counterbores 117 and corresponding ones of the bossbolt holes 118 extend axially parallel to the centerline 11 through thespinner 104 and each of bosses 110. Spinner bolts 120 are disposedthrough bolt hole 118 and are threaded into spinner nuts 122 swaged intothe forward bolt holes 100 in the annular forward flange 90 and securethe spinner 104 to the annular forward flange 90 and the disk 16. Thespinner nuts 122 are shank nuts which provide anti-rotation of the nutswhen swaged into the forward bolt holes.

An aft spinner flange 126 is attached to an axially aft spinner end 128of the aft conical section 109 of the spinner 104. A plurality of flangelightening holes 134 axially disposed through the aft spinner flange 126are circumferentially distributed around the aft spinner flange. Theflange lightening holes 134 are sized large enough with a largeclearance to allow the threaded forward shank portions of the platformpins 220 to easily pass through the flange lightening holes when thespinner is mated and fastened to the forward flange 90 of the forwardextension 86. The exemplary embodiment has more flange lightening holes134 than platform pins 220. The spinner 104 is illustrated herein ashaving a bi-conical shape having the forward conical section 107 and theaft conical section 109 connected by the transition section 108. Othershapes are contemplated by the present invention.

The platform pins 220 in the post holes 214 provide radial retention forthe forward portion of the platform.

The forward mounting lugs 40 of the platform 32 are trapped between theforward facing circular rim surface 142 of the rim 62 and the aftspinner flange 126, thus, providing axial retention for the platform asa whole.

While there have been described herein what are considered to bepreferred and exemplary embodiments of the present invention, othermodifications of the invention shall be apparent to those skilled in theart from the teachings herein and, it is therefore, desired to besecured in the appended claims all such modifications as fall within thetrue spirit and scope of the invention.

Accordingly, what is desired to be secured by letters patent of theunited states is the invention as defined and differentiated in thefollowing claims:

What is claimed is:
 1. A gas turbine engine blade spacer comprising: anaxially extending backbone, spaced apart forward, mid and aft dovetaillands, respectively, disposed along said backbone, a void extendingaround said backbone and between said forward and aft dovetail lands,said backbone and said forward, mid, and aft dovetail lands havingbottom curved backbone surfaces, and each of said forward, mid and aftdovetail lands having a riser that extends above said backbone andhaving a riser flat top.
 2. A spacer as claimed in claim 1 furthercomprising: said void filled with an elastomeric material, and aconstant cross-sectional area between said forward and aft dovetaillands.
 3. A spacer as claimed in claim 2 further comprising a spacer tabextending generally axially forward of said forward land and said tabhaving intersecting axially and radially extending tab apertures.
 4. Aspacer as claimed in claim 3 wherein said spacer tab has a rectangularcross-section, extends axially out of a forward face of said forwardland, and has a tab flat top that is co-planar with said riser flat topsof said risers.
 5. A spacer as claimed in claim 1 wherein said spacer isa circular arc shaped spacer and said backbone, and said forward, midand aft dovetail lands are curved along a circular arc normal to andabout a radial axis.
 6. A spacer as claimed in claim 5 furthercomprising: said void filled with an elastomeric material, and aconstant cross-sectional area between said forward and aft dovetaillands.
 7. A spacer as claimed in claim 6 further comprising a spacer tabextending generally axially forward of said forward land and said tabhaving intersecting axially and radially extending tab apertures.
 8. Aspacer as claimed in claim 7 wherein said spacer tab has a rectangularcross-section, extends axially out of a forward face of said forwardland, and has a tab flat top that is co-planar with said riser flat topsof said risers.
 9. A gas turbine engine blade spacer comprising: anaxially extending backbone, spaced apart forward, mid and aft dovetaillands, respectively, disposed along said backbone, said backbone andsaid forward, mid, and aft dovetail lands having bottom curved backbonesurfaces, each of said forward, mid and aft dovetail lands having ariser that extends above said backbone and having a riser flat top, anda spacer tab extending generally axially forward of said forward landand including intersecting axially and radially extending tab apertures.10. A gas turbine engine rotor disk assembly comprising: a number ofannular hubs circumscribed about a centerline, each of said hubsconnected to a disk rim by a web, a plurality of circumferentiallyspaced apart dovetail slots disposed through said rim, extendingcircumferentially between disk posts, extending axially from a forwardend to an aft end of said rim, and extending radially inwardly from adisk outer surface of said rim, a plurality of fan blades havingdovetail roots disposed in said dovetail slots, a plurality of bladespacers each of which is disposed within each of said dovetail slotsbetween a dovetail slot bottom wall and an axially extending root bottomsurface of said dovetail root, each of said blade spacers comprising: anaxially extending backbone, spaced apart forward, mid and aft dovetaillands, respectively, disposed along said backbone, a void extendingaround said backbone and between said forward and aft dovetail lands,said backbone and said forward, mid, and aft dovetail lands havingbottom curved backbone surfaces, and each of said forward, mid and aftdovetail lands having a riser that extends above said backbone andhaving a riser flat top.
 11. An assembly as claimed in claim 10 wherein:said dovetail slots are circular arc dovetail slots disposed throughsaid rim, said dovetail roots are circular arc dovetail roots, saidspacer is a circular arc shaped spacer, and said backbone, and saidforward, mid and aft dovetail lands are curved along a circular arcnormal to and about a radial axis.
 12. A gas turbine engine rotor diskassembly comprising: a number of annular hubs circumscribed about acenterline, each of said hubs connected to a disk rim by a web, aplurality of circumferentially spaced apart dovetail slots disposedthrough said rim, extending circumferentially between disk posts,extending axially from a forward end to an aft end of said rim, andextending radially inwardly from a disk outer surface of said rim, aplurality of fan blades having dovetail roots disposed in said dovetailslots, a plurality of blade spacers each of which is disposed withineach of said dovetail slots between a dovetail slot bottom wall and anaxially extending root bottom surface of said dovetail root, each ofsaid blade spacers comprising: an axially extending backbone, spacedapart forward, mid and aft dovetail lands, respectively, disposed alongsaid backbone, said backbone and said forward, mid, and aft dovetaillands having bottom curved backbone surfaces, each of said forward, midand aft dovetail lands having a riser that extends above said backboneand having a riser flat top, and a spacer tab extending generallyaxially forward of said forward land and including intersecting axiallyand radially extending tab apertures.
 13. An assembly as claimed inclaim 12 wherein said spacer further comprises: a void extending aroundsaid backbone and between said forward and aft dovetail lands, said voidfilled with an elastomeric material, and a constant cross-sectional areabetween said forward and aft dovetail lands.
 14. An assembly as claimedin claim 13 wherein said spacer tab has a rectangular cross-section,extends axially out of a forward face of said forward land, and has atab flat top that is co-planar with said riser flat tops of said risers.15. An assembly as claimed in claim 12 wherein said spacer furthercomprises: said void filled with an elastomeric material, and a constantcross-sectional area between said forward and aft dovetail lands.
 16. Anassembly as claimed in claim 15 wherein said spacer further comprises aspacer tab extending generally axially forward of said forward land andsaid tab having intersecting axially and radially extending tabapertures.
 17. An assembly as claimed in claim 16 further comprisingcircumferentially extending annular burst slots extending radiallythrough said rim into said dovetail slots between each adjacent pair ofsaid webs.
 18. An assembly as claimed in claim 17 wherein said forward,mid, and aft dovetail lands, respectively, are located along saidbackbone such that said burst slots are located between said forward,mid, and aft dovetail lands.
 19. An assembly as claimed in claim 18wherein said spacer tab has a rectangular cross-section, extends axiallyout of a forward face of said forward land, and has a tab flat top thatis co-planar with said riser flat tops of said risers.
 20. An assemblyas claimed in claim 19 further comprising: pairs of circumferentiallyoppositely facing retaining slots extending through overhangs ofcircumferentially adjacent pairs of said disk posts at an axial locationwhere said overhangs begin extending axially forward from said rim,retainers disposed in said pairs of retaining slots, said retainersextending across said dovetail slots so as to axially retain saiddovetail roots in said dovetail slots, and each of said retainers isradially supported by a corresponding one of said spacers and each ofsaid retainers includes a rectangular slot through which is disposedthrough said spacer tab.
 21. An assembly as claimed in claim 20 whereinsaid retainer includes a shelf radially below said slot and upon whichsaid spacer tab rests.
 22. An assembly as claimed in claim 21 furthercomprising: a radially extending shelf aperture disposed through saidshelf and aligned with said radially extending tab aperture, a spacerbolt having a spacer bolt head and a threaded spacer bolt shank, saidspacer bolt shank is disposed through said shelf aperture and saidradially extending tab aperture such that said spacer bolt head engagessaid shelf, and a spacer nut is threadingly secured on said spacer boltshank such that said spacer nut engages said spacer tab.